In a typical wireless network, many devices can communicate with each other. To facilitate communications between multiple parties or devices, communications must be managed. Thus, each network typically has a communications controller such as an access point, a piconet controller (PNC), or a station that acts as a controller and manages network communications. Each station, such as a personal computer, can associate with the controller and thereby associate with the network, connect to the network and gain access to resources connected to the network. Stations and network controllers typically utilize a network interface card (NIC) to make an associate and communicate with the network. To increase system efficiency, some wireless networks utilize omni-directional transmissions to associate and directional transmissions for transaction in data.
Many wireless networks utilize a frequency of 2.4 GHz for communicating as defined by the Institute of Electrical and Electronics Engineers ((IEEE)) 802.11b, and g specification. Other wireless networks utilize a frequency of 5 GHz for communicating as defined by the IEEE 802.11a specification. IEEE 802.11 a and b were published in 1999, and IEEE 802.11g was published in 2003. Stations that comply with the IEEE 802.11b standard may commonly be referred to or marketed as wireless fidelity (Wi-Fi) compatible devices. New wireless networks are being defined to operate in millimeter wave frequencies (e.g., 60 GHz band). Directional communications are important and in some cases required to achieve acceptable performance.
As stated above both omni-directional transmission and directional transmission are commonly utilized by wireless networks. An omni-directional transmission generally provides a traditional radiation pattern where the signal energy evenly propagates in a spherical nature or propagates evenly in three directions. A directional transmission can focus signal energy in a particular direction. More specifically, a directional transmission can operate more efficiently because more energy can be sent in the direction of the receiver while less energy is sent in directions where the signal is not intended to be received.
Likewise, a receiver can focus its receive sensitivity in a particular direction. Thus, a transmitter can focus RF energy in a direction of a receiver and a receiver can focus receive sensitivity in a particular direction to mitigate interferences and increase communication efficiency. A directional transmission system can provide improved performance over omni-directional systems. For example, directional systems can utilize significantly higher data rates. However, such systems may be more complex and more expensive than traditional omni-directional transmission systems. Directional antennas can have gains that are much higher than omni-directional antennas due to the narrower beam width, which focuses RF power to the receiving system and does not waste RF power in directions where there are no receiving devices.
State-of-the-art millimeter wave network communication systems typically utilize a low data rate, quasi-omni transmission during an association procedure. An association procedure between devices can be accomplished utilizing a physical layer protocol as defined by the open systems interconnect (OSI) specification published in 1980. Physical layer transmissions mode is the lowest layer in the OSI model and the physical layer can be utilized by devices to set up and manage communications. The physical layer specifies primarily transmissions of raw bit streams over the physical transport medium. Such a bit stream can be utilized by stations to recognize the existence of a compatible network and to associate with the network.
Interference caused by devices such as cell phones and appliances often cause communication links between networked devices to be dropped. Dropped communication links also result from the movement of stations or movement of obstructions. As stated above, many networks utilize directional transmissions, and although these network communication links can be more efficient than omni directional links, these links can be fragile due to station mobility and ever changing factors that produce interference. Such factors often can cause frequent, undesirable station or network disconnects.
A network system operating at low power in the Gigahertz range, for example at 60 GHz, is typically more susceptible to communication link drops that a system that operates at lower frequencies. This increased susceptibility is generally attributed to the inherent propagation characteristics of a radio wave in the air as higher frequencies encounter a higher oxygen absorption rate and increased attenuation. The attenuation may be caused by physical obstructions, particularly metallic obstructions between the transmitter and the receiver. Most link drops or disconnects require devices to commence a re-association process. Such a re-association process takes a relatively long time, slowing all network communications. Such a re-association process also significantly adds to network overhead where the resources are not exchanging data at high rates as is desired.
Thus, a network controller having many stations that are continually being dropped will have to re-associate with stations on a frequent basis. Such a process may require a controller to spend a significant amount of time and overhead managing and configuring communications where such time would be better spent transmitting and receiving data. When stations continually have to re-associate with a controller, more time can be spent on ministerial functions to manage network infrastructure than the time spent on actual data transfer, where data transfer is the end goal of the network. Accordingly network communication management is less than perfect.